The present invention relates to a data transmission device used together with a system interface such as a single-end type Small Computer System Interface (referred to as "SCSI" hereinafter) interface-bus connected in a so-called daisy chain type connection. In the system using such a transmission device together with a system interface, one apparatus transmits data to and/or data from another apparatus through the system interface.
SCSI is a standard high-speed parallel interface defined by the X3T9.2 committee of the American National Standard Institute (ANSI).
The term "daisy chain" means a set of devices connected in a series. When devices are daisy-chained to a microcomputer, the first device is connected to the computer, the second device is connected to the first, and so on down to the line. Signals are passed through the chain from one device to the next.
In an example of a small-scale computer system such as a personal computer system, such a system interface as SCSI is used to connect a host apparatus with peripheral system such as an external storing apparatus.
By utilizing a SCSI, as mentioned above, relatively high-speed data transferring is enabled. Further, by utilizing a SCSI in data transferring among several units/devices, various useful functions thereof may be utilized. Furthermore, effecting a single end type connection with a connection manner associated with the SCSI interface bus may simplify a composition of a system associated with the SCSI interface bus.
Such a computer system using SCSI for data transferring has a drawback that may appear when high-speed data transmission is executed through such a single-end type SCSI interface bus. This drawback consists of an insufficient signal level associated with a signal carried through the SCSI interface bus. This insufficient signal level results from the following causes. A first cause is an input capacity of a transistor included in a receiver unit. This receiver unit is used for inputting data from the SCSI interface bus. The second cause is a stray capacity of a printed circuit board which comprises circuits used to realize the function of the SCSI interface bus. The insufficient signal level may disable appropriate data transmission.